Yajnavalkya on Karma

“As a man acts, so does he become.
A man of good deeds becomes good, a man of evil deeds becomes evil.
A man becomes pure by pure deeds, ill by ill deeds.
Whatever desire he has, so is his will.
Whatever his will, so is his deed.
Whatever deed he does, that will he reap.”

Brihadaranyaka Upanishad 4.4.5 (Tr. Swami Nikhilananda)

An ancient Indian philosophical passage containing the earliest datable clear statement that a person's actions determine the nature of their rebirth.